Baking hydration percentage:
how bakers measure dough wetness

Water as a percentage of flour, not of the dough

Bakers describe a dough by comparing everything to the flour, which is always 100%. If a recipe uses 500 g of flour and 350 g of water, the hydration is 350 ÷ 500 × 100 = 70%. The water is measured against the flour alone, not against the total weight of the dough, which is why a hydration can be 80% or even 100% without the dough being 80% water.

The convention comes from baker's percentages. Salt, yeast and other ingredients are expressed the same way, so a 2% salt level in a 500 g flour recipe means 10 g. Because everything is a ratio to flour, a formula scales to any batch size by multiplying one number.

Counting a sourdough starter properly

A starter is itself flour and water, so it must be split into its parts. A starter fed at equal weights of flour and water is a 100% hydration starter: 100 g of it holds 50 g flour and 50 g water. Add that to the rest of the recipe before dividing.

Forgetting the starter's contribution is the commonest reason a sourdough recipe feels wetter or drier than its stated percentage. A stiffer starter at 60% hydration contributes less water: 100 g of it holds about 62.5 g of flour and 37.5 g of water, since 100 ÷ 1.6 = 62.5.

Milk, eggs, butter and honey

The same logic applies to anything wet. Whole milk is mostly water, commonly quoted as about 87%, while an egg is roughly 75% water. Butter is about 80 to 82% fat with a little water, and honey is around 17% water. Each recipe author decides how much of that to count, so pick a rule and apply it consistently.

• Simple method: count only plain water and milk as 100% liquid, ignore the water in butter and eggs.
• Strict method: multiply each ingredient by its water share and add it up.
• Whichever method you use, compare your dough only to recipes measured the same way.

In a bread with 500 g flour, 280 g water and 100 g milk, counting the milk fully gives 380 ÷ 500 = 76%. Counting only 87% of the milk gives (280 + 87) ÷ 500 = 73.4%. The difference is a few points, enough to change how the dough handles.

What different hydration ranges feel like

These ranges move with the flour. Whole wheat and rye absorb more water, so a 70% whole wheat dough feels stiffer than a 70% white one. Weaker flours also give up structure quickly at high hydration. If a recipe is new to you, begin near the lower end of its range and add a little water on the next bake.

Hitting a target hydration

To find the water for a target, multiply the flour weight by the percentage. For 500 g of flour at 75%, you need 0.75 × 500 = 375 g of water in total. If a 100 g starter provides 50 g of that, add 325 g of water at mixing.

Going from 70% to 75% on a 500 g flour recipe is only 25 g more water, about two tablespoons, which is why small changes show up so clearly. Add water gradually during mixing, since flour absorbs at different speeds, and note the final amount so that you can repeat it.

From a target dough weight to ingredient grams

Baker's percentages become practical when you know how much dough you want. Add the percentages of every ingredient to get the dough's total percentage, then divide the target weight by it to find the flour. Take a 70% hydration dough with 2% salt: flour is 100%, water 70%, salt 2%, a total of 172%.

This is how professional bakeries scale formulas from one loaf to several hundred. It also explains why a hydration change is easy: the same flour weight with 75% instead of 70% means 436 g of water and a dough about 29 g heavier, so you can anticipate the result before you mix.

Limits of the number

Flour itself is another variable. Protein content, bran, and the way it was milled all change how much water it can hold. Many bakers keep a note beside each recipe naming the flour used, since a switch of brand can move the comfortable hydration by 3 to 5 points without any change to the written formula.

Hydration says how much water is present, not how the dough will behave. Autolyse, mixing time, temperature and gluten development each change handling. Two doughs at 72% can feel quite different, and in the same kitchen a humid day can make the same recipe slacker.

A hydration calculator is a quick way to turn a recipe from cups into grams or to check a starter, but the dough in your hands makes the final call. Write down the hydration with each bake and what you noticed; within a few loaves, the percentage becomes a language you can read.